In today's society, people pay more and more attention to the protection of their privacy. In many cases that the resident status is needed to be verified, it is undesired for a person that his identity information is disclosed to an authenticator while the legality of the identity information is verified, so adequately protecting the privacy is required. For example, in the case that a vote is taken on some sensitive issues, a voter not only hopes to complete the vote by his legal identity, but also does not hope to expose his identity. In some consumption occasions, a consumer does not hope that his personal information is tolerant by a merchant when a payment is made. After logging on to the network by a controllable identity, a network user does not hope that his identity information is disclosed to the public in many cases. Presently, the demand for protecting such privacy becomes more and more apparent.
There are many kinds of techniques for proving identity authentication service. Presently, the identity authentication method based on public-key cryptography is commonly used. This method verifies the legality of the identity of the peer by means of a digital signature, while the identity information of the peer is disclosed to the authenticator. Apparently, there is limitation for such technique when it is used to provide the authentication service in the above-mentioned applications, thus it can not protect the user's privacy. In another respect, it is necessary to provide traceability by the identity authentication technique which provides privacy protection, such that an administrator can perform control as needed.